Chapter 3: How much? Flashcards
What is AR?
Relative atomic mass
How do you work out Relative atomic mass of a compound
Find the Mr of the molecule - Add up the Ar’s of each atom
Why is a mass spectrometer better than paper chromotography?
It is quicker, more accurate and can Identify very small amounts
How do you work out percentage of an element in a molecule?
Ar of the element in the molecule / Mr of the whole molecule
How do you work out the mass of a mole of any element?
It is the same as the Atomic number (e.g. 1 mole of oxygen is 16 grams)
How do you work out the mass of a mole of any compuound?
It is the same as the Mr.
What is the empirical formula of a molecule?
The simplest ratio of elements (eg, C2H4 —> CH2)
How do you convert mass into moles
Mass/Ar
How do you figure out empirical formula by mass?
Convert each element’s mass into moles. Divide each amount by the smallest value to get a simple ratio. Write the formula by that ratio.
How do you figure out empirical formula by percentage
Replace the % signs with grams and work out as usual.
How do you work out percentage yield?
Amount produced/maximum possible.
What is the minimum energy required for a chemical reaction called?
Activation energy
